The present invention is applicable to all mass chambers no matter whether the mass chamber is part of a cooling zone, a cooling level, a crystallization zone, a crystallization level, a reheat zone, a reheat level or the like. The tempering medium may either be a cooling medium or a heating medium. Usually, the tempering medium is water. Nevertheless, the cooling medium may also be a medium different from water. The present invention is applicable no matter whether the tempering chambers adjacent to the mass chamber are connected to one and the same, or to different tempering circuits.
An apparatus for continuously tempering chocolate masses and the like is known from U.S. Pat. No. 4,648,315. The apparatus includes a tempering column including flat elements being arranged one above the other. A tempering chamber through which a tempering medium flows and a mass chamber through which the mass to be tempered flows are alternatingly arranged in the tempering column. The chambers are designed as disc-like hollow bodies. The tempering chambers are connected to tempering circuits. The mass chambers are interconnected for the flow of the mass from one mass chamber to the next mass chamber. The mass exits a first mass chamber and it enters the adjacent mass chamber in the region of the inner circumference of a driving shaft extending along the axis of the tempering column. Each mass chamber includes two disc-like bodies being driven by the driving shaft. At their outer circumference, the two disc-like bodies include openings for the mass to pass from the bottom side of the first disc-like body to the top side of the second disc-like body. The two disc-like bodies include spiral-like stripping ridges being longer than the radius of the disc. The ridges are arranged at a sense of rotation such that they subject the mass to a conveying effect. Two adjacent spiral-like stripping ridges form a channel continuously extending from the outside to the inside of the disc. The mass is conveyed through this channel without having the possibility of getting in contact with mass being located in other channels. The stripping ridges take the mass off the tempering surfaces of the chamber without getting in direct contact to the tempering surfaces. The two disc-like bodies include ridges at their adjacent sides in each mass chamber. The ridges are radially arranged, and they substantially extend from the inside to the outside in a continuous manner to provide a mixing effect to the mass. There is the danger of so-called dead zones of non-moving or stationary mass being formed between the disc-like bodies. Consequently, if these dead zones are built, the mass only flows across the outer sides of the disc-like bodies facing the tempering surfaces. The two discs being arranged inside the mass chambers do not provide a substantial mixing effect to the mass.
It is also known in the art to only use one disc-like body in each mass chamber. The driven disc includes openings at its outer circumference for a passage of the mass from the bottom side of the disc to the top side of the disc. Both surfaces of the disc include spiral-like stripping ridges. Adjacent stripping ridges form a channel providing a conveying action to the mass. The stripping ridges take the mass off the tempering surface to convey the mass from the inside to the outside, and from the outside to the inside, respectively. The mass exits a first mass chamber and enters a second mass chamber in the inner region of the disc, i.e. close to the driving shaft. Due to channels being formed, the stripping ridges provide a substantial conveying action for the mass. There is no substantial mixing of the mass. Thus, different mass particles at different distances with respect to the tempering surfaces have different temperatures. Consequently, there is the danger of the critical temperature at which crystals are formed in a cooling zone or in a crystallization zone being exceeded. When such a mass chamber and a tempering chamber, respectively, is utilized in the region of a cooling zone or of a crystallization zone, there is no guarantee that a sufficient number of steady B-crystals is formed. B-crystals determine the crystallization of the mass to be tempered and the quality of the product to be produced.
Apparatuses for continuously tempering chocolate masses and the like are known from the European Patent Application No. 0 289 849 A2 and the European Patent Application No. 0 806 149 A2. The apparatuses include a tempering column including a majority of chambers forming a cylinder. The chambers are partly connected to a cooling circuit for a cooling medium, and they are partly connected to a heating circuit for a heating medium. A mass chamber through which the mass flows is arranged between two adjacent chambers. The mass chamber is limited by tempering surfaces being formed by the two adjacent chambers. A driven mixing tool is arranged in each of the mass chambers. The mixing tool includes a hub and a number of radially extending arms. The number of arms usually is between 2 and 4. Each arm includes mixing blades at its top side and its bottom side. The mixing blades provide a mixing motion to the mass. The mixing blades also fulfil the function of taking the mass off the tempering surfaces. The mixing blades are arranged to be radially overlapping. The mixing blades may have an elongated, a convex or a concave design. The design and arrangement of the mixing blades is always identical on one side of the arms, while the design and arrangement of the arms may be identical on the other side, or it may just be opposite. The arms may also include openings to have a positive influence on the mixing effect. The mixing blades fulfill the taking off function and the mixing function. The substantial conveying function is provided by a mass pump pumping the mass through the apparatus and from a first mass chamber to a second mass chamber. There may be regions at different locations inside the mass chambers in which the mass particles remain for different periods of time. There is no guarantee that the mass first entering the apparatus also first exits the apparatus. Due to the arrangement of the mixing arms, there is the danger of the mass remaining in the mass chamber in a circular movement, and thus not participating in the streaming motion of the mass through the apparatus. Different temperatures may occur in differently moved portions of the mass. When the connecting points at which the mass passes from one mass chamber to the adjacent mass chamber is always located on the outside, meaning in the region of the outer circumference of the disc-like mass chamber, there is the danger of a so-called short stream of the mass through the apparatus. Regions of the mass chamber being located at a comparatively small radius do not participate in the flowing motion. This is also true when the mass passages between two mass chambers are spaced apart by 180.degree..